Neutrophils are the major cellular immune components in response to bacterial infections. Neutrophil enzymes are important in invasion, inflammation, and infection processes. In order to understand the basic effects of protein malnutrition on neutrophils we studied matrix metalloproteinases 8 and 9 (MMP-8 and MMP-9) production in severe quantitative and qualitative protein malnutrition in rats. Wistar rats (2 months old) were divided into four groups each with three subgroups and fed various protein-containing diets (24% protein, 20% gelatin-containing and N-free) for 7, 14, 21, and/or 28 days. Neutrophil enzyme expression was determined by Western blotting. Leukocytes decreased significantly due to malnutrition (p = 0.001 ) whilst the percentage of neutrophils increased (p = 0.02) in protein-deprived groups. Neutrophils of malnourished rats produced lower levels of MMP-8 at early stages of protein deprivation with an increase in the following weeks. MMP-9 production by neutrophils from N-free diet fed animals was highest after one week. Serum MMP-9 levels decreased in the qualitative but not in the quantitative protein malnutrition groups. Results suggest that neutrophils might be important in reuse of body cell proteins during fasting or malnutrition conditions and dietary manipulation might have profound effects on MMP-8 and -9 production in rats.